Maverick and DBS temperature discussion

[AggieBQ72]

Now that I've cooked several things in my DBS, I have noticed something about the temperature controls using the Maverick.  If I set the DBS oven temp to 210F, the Maverick will show the temp go from 210 up to 260F and then drop slowly back to 210F.  I assume that the heating element turns on long enough to heat it up to 260 and then when it turns off the temp drops to 209 and the heating element comes back on.  I guess in my "analytical mind" that I was thinking that 210 meant 210 all the time but I see why it has to heat it up hotter and then manage to catch the lower temp and start back up again.  In this case, would you say that you are cooking at 210 ..... 260.....or take an average and go 235F? 

If you read that someone smokes at brisket at 250F, would that indicate the minimum temp that was always maintained was 250 or the highest temp that the oven obtains or the average temp.  If the latter then you would have to estimate the average temp and then calculate a new temp to set the DBS oven temp.

Again, I come to this with a purely analytical mind when 210 means 210 and I know in the real world of smoking this is probably not the case.  I know that you have to have the oven temp higher than the expected internal meat temp or you will never get anything smoked and done.

[westexasmoker]

I am by no means an expert on this, espiecially since in run an OBS, but seems llike I remember that the DBS operates much like your home thermostat and will do just as you describe overshoot the set temp and come back down, then back up again.  Kinda had that same issue with my OBS, granted it was operator induced....the PID solved all of the temp swing problems!  Hope that helps, someone with more knowledge will be along I'm sure!  Good luck!

C

[KyNola]

Aggie,
I too have have the BDS and experience the same wild swings you describe.  That is exactly why I have the Maverick as the BDS temp sensor in the box is not all that accurate.  You will find that the temp swings occur much more widely when the load is first placed in the box.  As the meat comes up to temp, the swings decline and your Maverick and the BDS digital reading will be very close to each other.

As for your question about the statement of someone smoking at 250, I take that to mean that they set the BDS to that temp, experience the wide swings you described until the meat begins gaining temp and the swings lessen.

Experience is a great teacher of lessons.  You'll get the hang of it and how to compensate.  Hope this helped some.

KyNola

[Gizmo]

I don't consider myself an expert but here is my 2 cents worth.
The temp sensor for DBS is located around the middle of the box.  The sensor is probably not a very fast sensor in that it probably takes several minutes for it to actually read the temperature.  The heating element is located at the back bottom of the unit, under the V tray.  The V tray will block some of the heat.
The heating element appears to cycled on or off so when it is on, max heat is going out.
Meat or other products being smoked, absorb heat and also block heat from the sensor.
With the location of the sensor, the heat blockage from the V tray and the food, the absorption of heat by the food, the slowness of the temperature sensor, and the max on or off of the heating element, it is not unreasonable for there to be large temperature swings. 
On my last smoke, I smoked a 6-8 lb brisket flat.  I had the maverick oven temp probe on the same rack just to the left of the brisket in open space.  I had the poulder dual probe stuck into the brisket so that the probe tip would monitor the meat and the base of the probe monitor the cabinet temperature.  Now the two probes are only 8 to 12 inches from each other.  One unobstructed and the other obstructed by the meat.  The Maverick and the DBS measured close to each other (the rack was at about the same height as the DBS senor in the middle of the box).  There was a 50 to 60 degree difference between the Maverick and the Poulder over the first 2 to 3 hours.  It started getting closer as the meat temperature came up.  I have done this numerous times before and always see similar results.  I usually place the Maverick Probe on the same shelf as the meat (without touching) and use it to judge the actual oven temperature. 

The PIDs have an advantage in my opinion in that they have a faster reacting sensor and are locatable to the user's desired placement.  Some also can vary the heating temperature (ramp) so they can maintain a better overall average.

Now for my bottom line.  The OBS and the DBS have been successfully used for many years with those temperature swings, without modifications, and produce great results.  Most food smoked do not need super tight temperature control.  The Bradley is merely an oven after the smoke is applied.   PIDs are a great mod especially if you are doing sausages and need a tighter control although you can still get good results with out it. 

For those with PIDs, has anyone measured the temperature above and below a large quantity of meat and from top to bottom within a large load?  From my reasoning, the PID would only solve one of the variations and therefore there would still be a significant difference in temperature between the top and bottom of a large piece of meat.   Which is why several have added a stir fan for ciculation but even with that, the space available for such a device does not allow the design to be such that it can provide a good quality convection like environment.

[Mr Walleye]

For those with PIDs, has anyone measured the temperature above and below a large quantity of meat and from top to bottom within a large load?  From my reasoning, the PID would only solve one of the variations and therefore there would still be a significant difference in temperature between the top and bottom of a large piece of meat.   Which is why several have added a stir fan for ciculation but even with that, the space available for such a device does not allow the design to be such that it can provide a good quality convection like environment.

In my opinion you are absolutely correct. You want to read or, in the case of a PID, control the heat your meat is exposed to. This means taking the temp reading before the meat has time to influence the temperature. There is no question that the meat itself influences the temps both beside and above it because it is absorbing the heat, giving off cold and giving off moisture. Certainly adding the circulation fan helps this but doesn't eliminate it. I know when I used to do jerky completely on the Bradley (prior to adding a circulation fan) I would rotate the racks several times. After adding the circulation fan I would only rotate once or twice. To me it's all about reading the temp the meat is exposed to, which means you should be taking the tower temp just below the meat.

I think the temp readings on the DBS is influenced by the meat a fair bit as well because the sensor is located very close to the second rack (counting up). As the IT of the meat rises the accuracy of the DBS improves because the meat has less influence on the tower temperatures.

At least that's my 2 cents anyway...

Mike

[pensrock]

I know its not like me when it comes to temperature controllers, but I really have nothing to add.  :)

If you need or just want very tight control over the temp, then a PID is the way to go. But like was mentioned earlier many OBS and DBS smokers are out there with no modifications making wonderful food. Since I work with temperature controllers about every day. I made a PID and can now keep +-1 degree control. Do I need +-1 degree control? Of course not but I do like at least +-5 for doing sausage etc.